High Efficiency Low Pressure Drop Synthetic Fiber Based Air Filter Made Completely From Post Consumer Waste Materials

ABSTRACT

A non-woven textile based filter media is produced from polyester fiber generated using recycled polyethylene terephthalate (PET) beverage bottles, and that non-woven textile based filter media is used to make an air filter. By controlling the diameters and lengths of the PET derived polyester fibers, a non-woven textile based filter media that exhibits a natural Minimum Efficiency Reporting Value (MERV) of about 8 (without requiring electrostatic treatment) and a pressure drop of 2.9 PSI or less can be achieved. A related exemplary embodiment is an air filter fabricated entirely from recycled materials, including a recycled cardboard frame, the non-woven textile based filter media made from recycled PET derived polyester fibers, and a support structure made of recycled plastic or metal wire.

RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No.12/850,509, filed on Aug. 4, 2010, entitled “High Efficiency LowPressure Drop Synthetic Fiber Based Air Filter Made Completely From PostConsumer Waste Materials”, which is hereby incorporated by reference inits entirety.

U.S. patent application Ser. No. 12/850,509 is based on a priorco-pending provisional application Ser. No. 61/231,206, filed on Aug. 4,2009, the benefit of the filing date of which is hereby claimed under 35U.S.C. §119(e).

BACKGROUND

Air filters are often rated using a Minimum Efficiency Reporting Value(MERV) rating; an industry standardized numerical value used to quantifyan air filter's filtering ability. The MERV rating allows consumers tocompare the ability of different air filters to capture and hold dirtand dust in specific size ranges. Higher MERV ratings mean fewer dustparticles and other airborne contaminants pass through the filter.

Air filters for residential use often have relatively low MERV ratings,ranging from about MERV 1 to about MERV 4. Such air filters aregenerally incapable of removing particles smaller than about 10 microns.Air filters having a MERV rating ranging from about 5 to about 8 arecommonly used as high end residential air filters and for commercialapplications, and such air filters will collect particles as small as 3microns. Air filters having a MERV rating ranging from about 9 to about12 are commonly used in commercial and industrial applications, and willstop particles in the 1 to 3 micron range. The most efficient airfilters have MERV ratings of about 13 to about 16, and such air filterswill stop particles as small as 0.3 microns. These air filters are usedin hospitals and other super clean environments.

Particularly in commercial heating, ventilation, and air conditioning(HVAC) applications, the amount of energy required to move air throughall of the air filters in a system can be significant. Even where twoair filters have the same MERV rating, those two air filters may requiredifferent amounts of energy to force air through each of the twodifferent air filters. The relative air resistance of an air filter canbe measured by determining a pressure drop across the air filter. Airfilters having relatively lower pressure drops will require less energyto drive air through the air filter.

While many different types of air filters are known, to date there areno air filters available that combine the characteristics of (1) beingmade entirely from recycled materials; (2) exhibiting a desirable MERVrating; and (3) exhibiting a relatively low pressure drop. It would bedesirable to provide such an air filter.

SUMMARY

This application specifically incorporates by reference the disclosuresand drawings of each patent application identified above as a relatedapplication.

The concepts disclosed herein encompass air filters that combine thecharacteristics of (1) being made from recycled materials; (2)exhibiting a desirable MERV rating (in at least one exemplaryembodiment, a MERV rating of at least 8); and (3) exhibiting arelatively low pressure drop (in at least one exemplary embodiment, apressure drop of less than 2.9 PSI). In at least one embodiment, thefilter media used in the air filter is made from synthetic fibersgenerated entirely from post consumer waste materials. While virginsynthetic fibers could be employed to produce the filter media disclosedherein, purchasers of the air filters disclosed herein may prefer“green” (i.e., environmentally friendly) air filters made from recycledmaterials, over air filters made from virgin materials.

In at least one embodiment, the synthetic fibers are provided in aspecific range of lengths, and relatively shorter and relatively longerfibers are combined together into a mass. The mass is then processedinto a non-woven textile or fabric, such that the textile or fabric isused as the filter media. Needle-based felting, or needle punching, canbe used to generate commercial quantities of a textile having thepreferred range of lengths. Such a non-woven textile represents anexemplary textile for implementing the concepts disclosed herein; assuch non-woven textiles are much easier to manufacture than woventextiles. With respect to the preferred range of lengths, the longerfibers act as a natural binder to give the resulting textilecohesiveness, while the shorter fibers ensure that the resultingnon-woven textile includes a large number of interstitial spaces forcapturing contaminants.

With respect to embodiments employing a mixture of different lengthfibers, empirical testing has determined that fiber lengths ranging fromabout 5 mm to about 100 mm are most preferred to achieve these enhancedstructural properties. A substantial majority of the fibers preferablyrange from about 5 mm to about 55 mm in length, and most preferably,about 70% of the fibers fall into the aforementioned range of lengths.The length of a minority of the fibers is in the range of from about 60mm to about 100 mm, and most preferably, less than about 30% of thefibers are in this range. Regardless of the specific range employed, asubstantial majority of the fibers must be relatively shorter to providethe desired large surface area, and the desired plurality ofinterstitial volumes or spaces. Also, regardless of the specific rangeof lengths of the fibers, sufficient relatively longer fibers arerequired to enable the wadded mass to achieve a cohesiveness thatenables a mat formed out of the wadded mass of fibers to exhibitsufficient structural stability to withstand the air flow rates used inair filtering applications. It should be recognized that while the fiberlengths discussed above represent exemplary lengths used in someembodiments disclosed herein, other embodiments disclosed herein employdifferent fiber lengths, and some embodiments disclosed herein employdifferent ratios of fiber lengths.

The ratio of short fibers to long fibers is important in providing ahigh efficiency filter media. A majority of short fibers increasesorbency by increasing the total surface area of the sorbent and byensuring that the mass of fibers (in a textile formed from the mixtureof fiber lengths) includes a relatively large volume of interstitialspaces for absorption of a material. However, if only short fiberlengths are employed, the resulting mass of short fibers will exhibitvery little mechanical strength, such that the mass will be easilybroken up and dispersed by even modest air pressure. Thus, a mass ofonly the short fibers, when formed into a non-woven textile, would notbe suitable for use as an air filter, because the mat would disintegratewhen exposed to modest air pressure. Industry standard for air filtersis based on an air flow rating of about 1968 cubic feet per minute, sofilter media used in air filter must at a minimum be able to maintaincoherency at such an air flow rate. Industry standard for air filters isbased on an air flow rating of about 1968 cubic feet per minute, sofilter media used in air filters must at a minimum be able to maintaincoherency at such an air flow rate. This is very important, as if an airfilter media made out of fibers were to begin to fall apart at such airflow rates, loose fibers could get sucked into the air moving equipment,causing significant damage to expensive mechanical components.Sufficient longer fibers should be included to enable a morestructurally stable and stronger network of fibers to be achieved inaccord with the concepts disclosed herein, particularly where themixture of fiber lengths include relatively short fibers (i.e., fibersof less than about 15 mm in length).

In addition to carefully controlling the fiber lengths, fiber diametersare also carefully controlled in at least some embodiments disclosedherein. In at least one embodiment, the fiber diameter used to producethe filter media is 1.5 denier. Denier is a unit of measure for thelinear mass density of fibers, defined as the mass in grams per 9,000meters. A fiber is generally considered a microfiber if it is 1 denieror less. A 1 denier polyester fiber has a diameter of about 10micrometers. In at least one embodiment, the fiber diameter used toproduce the filter media is 4 denier. In a related embodiment, thefilter media is made from a mixture of 1.5 denier and 4 denier fibers.

Yet another aspect of the concepts disclosed herein is directed to amethod of recycling post consumer waste into a sorbent product. Therecycling industry has matured such that plastic beverage bottlesrepresent an ongoing waste stream. Such bottles are often made ofpolyethylene terephthalate (PET). PET bottles can be converted intopolyester fibers of specifically defined diameters, which can beprocessed into the exemplary lengths discussed above (as well as thelengths discussed below in other embodiments). Once the desired mixtureof fiber lengths (and/or diameters) are achieved, the fibers are cardedand needle punched to produce a non-woven textile.

In an exemplary air filter embodiment, the filter media (i.e., thenonwoven textile) weighs from about 3.5 to about 4.5 ounces per squareyard, and can range from about 0.0625 inches in thickness to about 0.180inches in thickness (when in the form of a non-woven pad or mat). In yetanother exemplary air filter embodiment, the filter media (i.e., thenon-woven textile) weighs from about 0.15 to about 0.35 ounces persquare foot, and can withstand air flow rates of about 1968 CFM orgreater.

In a related embodiment, the frame and support structure for the airfilters disclosed herein can also be fabricated from recycled materials.The frame can be cardboard that is fabricated from recycled materials,and the support structure can comprise a plastic screen or metal wiremesh (also fabricated from recycled materials). Thus, one aspect of theconcepts disclosed herein is directed to an air filter fabricated from100% recycled materials.

In a related embodiment, in addition to using PET bottles to produce thefilter media, fabric and textile waste including a majority of syntheticfibers (including but not limited to clothing, carpet, drapery, linens,tents, and sleeping bags) is shredded to produce synthetic fibers (andin some, but not all exemplary embodiments, such non PET derived fiberis provided in the mixture of relatively long and short fibers discussedabove). Where such other waste streams are used to produce recycledsynthetic fiber, the non PET derived synthetic fibers should be used incombination with a majority of PET derived polyester fiber. In otherwords, only relatively smaller amounts of non PET derived recycledsynthetic fibers should be used. In an first exemplary embodiment, about90% or more of the synthetic fiber used in the filter media for the airfilter will be PET derived polyester fiber. In a second exemplaryembodiment, about 75% or more of the synthetic fiber used in the filtermedia for the air filter will be PET derived polyester fiber. In a thirdexemplary embodiment, about 50% or more of the synthetic fiber used inthe filter media for the air filter will be PET derived polyester fiber.With respect to synthetic fiber from non PET bottle recycled sources,most of the non PET recycled synthetic fiber will have been delustered(a process that changes the sheen of the synthetic fibers, and whichfacilitates dying the synthetic fibers). Delustering increases thesurface area in the resulting non-woven textile, increasing theeffectiveness of the non-woven textile as a filter.

In a related embodiment, an air filter using a recycled synthetic fiberfilter media based on one or more of the embodiments discussed aboveincludes a cardboard frame and a mesh support structure, and exhibits aMERV of 8 without any electrostatic treatment (i.e., a natural MERV 8,noting that filter media can be electro-statically charged totemporarily increase the MERV rating of the filter; however, suchelectrostatic treatments fade over time), and exhibits a pressure dropof less than 2.9 PSI.

In a related embodiment, an air filter using a recycled synthetic filtermedia as discussed above includes a cardboard frame and a mesh supportstructure, and the PET derived polyester based filter media has beentreated with at least one of a herbicide, a bactericide, a fungicide, anantimicrobial agent, a deodorizer (such as activated carbon, or othermaterials, to remove odors), and a fragrance (to introduce a pleasantscent into the filtered air).

In a related embodiment, an air filter using the PET derived polyesterbased filter media discussed above includes a cardboard frame and a meshsupport structure, and the PET derived polyester based filter media hasbeen treated with an electrostatic charge to increase its MERV value.

This Summary has been provided to introduce a few concepts in asimplified form that are further described in detail below in theDescription. However, this Summary is not intended to identify key oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

DRAWINGS

Various aspects and attendant advantages of one or more exemplaryembodiments and modifications thereto will become more readilyappreciated as the same becomes better understood by reference to thefollowing detailed description, when taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 schematically illustrates an air filter made entirely of recycledmaterials, incorporating a non-woven textile (made of PET derivedpolyester fibers having predefined lengths and diameters);

FIG. 2 schematically illustrates an exemplary air filter made entirelyof recycled materials, incorporating a pleated non-woven textile;

FIG. 3 is a flow chart indicating a sequence of exemplary steps toproduce a non-woven textile filter media made of PET derived polyesterfibers for use in the exemplary air filters of FIGS. 1 and 2;

FIG. 4A is a schematic view of a relatively shorter PET derivedpolyester fiber that comprises the majority of a non-woven textilefilter media in an exemplary embodiment;

FIG. 4B is a schematic view of a relatively longer PET derived polyesterfiber that comprises the minority of a non-woven textile filter media inan exemplary embodiment;

FIG. 5A is a schematic view of a relatively wider PET derived polyesterfiber that comprises the minority of a non-woven textile filter media inan exemplary embodiment;

FIG. 5B is a schematic view of a relatively thinner PET derivedpolyester fiber that comprises the majority of a non-woven textilefilter media in an exemplary embodiment;

FIG. 6 is a schematic view of a plurality of relatively longer PETderived polyester fibers intermingled with a plurality of relativelyshorter PET derived polyester fiber to form a non-woven textile filtermedia in accord with the concepts disclosed herein;

FIG. 7 is an enlarged view of a portion of the schematic view of FIG. 6,illustrating adsorption on the surfaces of both the plurality ofrelatively longer PET derived polyester fibers and the plurality ofrelatively shorter PET derived polyester fibers, as well as absorptionat a plurality of interstitial spaces within the nonwoven textile filtermedia; and

FIGS. 8A and 8B schematically illustrate air filters where the supportstructure exhibits a different configuration than that shown in FIG. 1.

DESCRIPTION Figures and Disclosed Embodiments Are Not Limiting

Exemplary embodiments are illustrated in referenced Figures of thedrawings. It is intended that the embodiments and Figures disclosedherein are to be considered illustrative rather than restrictive. Nolimitation on the scope of the technology and of the claims that followis to be imputed to the examples shown in the drawings and discussedherein. Further, it should be understood that any feature of oneembodiment disclosed herein can be combined with one or more features ofany other embodiment that is disclosed, unless otherwise indicated.

As used herein and the claims that follow, the terms about andapproximately are intended to refer to a range plus or minus 10% of astated value. Thus, about 100 and approximately 100 should both beunderstood to encompass a range of 90 to 110.

Overview of the Concepts Disclosed Herein

An effective air filter, having a desirable MERV rating (in an exemplaryembodiment, MERV 8 or above) and a relatively low pressure drop (in anexemplary embodiment, a pressure drop of less than 2.9 PSI) can be madefrom entirely recycled materials. A key component of such an air filteris a non-woven textile filter media formed out of PET derived polyesterfibers. While many different configurations of synthetic fibers can beused to achieve an air filter having a MERV rating of 8 or higher,providing an air filter combining such a MERV rating with a relativelylow pressure (i.e., less than 2.9 PSI) is surprisingly difficult. Thepressure drop aspect is significant, in that reducing the pressure dropcan lead to significant energy savings. For example, a relatively moreexpensive air filter having a relatively lower pressure drop mayactually be more economical to use, once energy costs are factored in.Details of an exemplary non-woven filter media based on PET derivedpolyester fibers that can be used to achieve an air filter having arelatively low pressure drop are provided below.

Exemplary Air Filters Made Entirely from Recycled Materials

Referring to FIG. 1, an air filter 80 includes a cardboard frame 82, aPET derived polyester fibers based filter media 84, and a supportstructure 86. The filter media is based on recycled PET derivedpolyester fibers that have been used to generate a non-woven textile.Exemplary filter media, produced by controlling the source of the fiber,the diameter of the fiber, and the length of the fiber, are discussed indetail below. The selected fibers are formed into a non-woven textile,such as a mat or pad. Needle punching represents an exemplary techniquefor forming the non-woven textile. Felting or thermal bonding are lesspreferred, as such techniques generally undesirably increase thepressure drop exhibited in the resulting filter material. The supportstructure can be a relatively coarse plastic or wire mesh, which ispositioned on the air flow exit side of the filter media. Note thatrelatively coarse meshes are preferred, because relatively tight mesheswill undesirably increase the filter's resistance to airflow. In anexemplary embodiment, the frame and support structure can be fabricatedfrom recycled materials. Thus, one aspect of the concepts disclosedherein is an air filter fabricated entirely from recycled materials.

The non-woven textile filter media for the exemplary air filtersdisclosed herein can be in a flat panel, or a pleated form. FIG. 2schematically illustrates an exemplary air filter including a cardboardframe 82, in which filter media 84 a is arranged in a pleatedconfiguration. Those of ordinary skill will recognize that the number ofpleats can be varied in size and density as desired.

Exemplary Filter Media for Use in an Air Filter Having a Low PressureDrop

Applicants initially attempted to develop an air filter using recycledsynthetic delustered fibers generated by reducing textile waste, fabricwaste, and clothing waste to fiber form. While that material, marketedunder the trade mark X-TEX™, is very effective as a filter media forremoving oil from water, when used as an air filter, the pressure dropexhibited by the filter media was higher than desired.

When marketed for use as a filter media for removing oil from water,XTEX™ is available as a non-woven textile having a density of about 12ounces per square yard. Air filters using filter media made out ofX-TEX™ having that density did exhibit a very satisfactory MERV 8rating, but also exhibited a pressure drop over 3.8 PSI, indicating thatsuch an air filter would not be very commercially viable due to theavailability of lower pressure drop air filters having similar MERVratings. Reducing the density of the X-TEX™ non-woven textile to about 6ounces per square yard, and then again to about 4.5 ounces per squareyard, resulted in air filters having MERV ratings of about 8, withsomewhat lower pressure drops; but the pressure drops for such airfilters still exceeded 3.5 PSI. Reducing the density of the X-TEX™non-woven textile even lower resulted in a filter media that was notsufficiently durable to function as a filter media in an air filter.

Applicants determined that the structure of the non-woven filter mediais very important in achieving a relatively low pressure drop. While anon-woven fabric made from a generic synthetic fiber can be used as afilter media for an effective air filter, unless great care is taken indesigning the structure of the non-woven fabric, it is difficult toachieve an air filter having a relatively low pressure drop. Extensiveempirical testing has indicated that achieving an air filter having acombination of a desirable MERV rating (in an exemplary embodiment, MERV8 or above) and a relatively low pressure drop (in an exemplaryembodiment, a pressure drop of less than 2.9 PSI) requires carefulselection of the source of the synthetic fibers used to produce thenon-woven fabric filter media, the relative lengths of the syntheticfibers employed in the non-woven fabric filter media, the relativediameters of the synthetic fibers employed in the non-woven fabric, andthe relative density of the resulting non-woven fabric filter media.Careful control of such parameters is necessary to achieve the desiredcombination of MERV rating and pressure drop. Exemplary combinations ofthese parameters will be provided below, after discussing an exemplarysource for recycled synthetic fibers.

Applicants discovered that a recycled synthetic fiber based filter mediaexhibiting the desired combination of a MERV rating of 8 or higher and arelatively low pressure (i.e., less than 2.9 PSI) can be achieved byusing polyester fiber recovered from PET beverage bottles, if the fiberdiameter and fiber lengths are controlled as discussed below. FIG. 3 isa flow chart indicating a sequence of exemplary steps to produce anon-woven textile filter media made of PET derived polyester fibers foruse in an air filter having a MERV rating of 8 and a pressure drop ofless than 2.9 PSI.

In an optional block 90, PET bottles are sorted by color. While thecolor of the resulting polyester fiber is not important from aperformance standpoint, from a marketing standpoint color may be animportant parameter to control. For example, end users may falselyconsider variations in color to be an indicator of lower quality.Control of the color of the PET bottles used will enable colorvariations among different batches of PET derived polyester fiber to bereduced. In at least one exemplary embodiment, green PET beveragebottles are employed, so that the resulting PET derived polyester fiberis green in color. From a marketing standpoint, this emphasizes thegreen (i.e., environmentally friendly) nature of the resulting airfilter, because the filter media used in the air filter is literallygreen in color.

In a block 92, the PET beverage bottles are converted to fiber.Different fiber manufactures may employ different production techniques,thus the following production technique should be considered to beexemplary, and not limiting, so long as the resulting PET derivedpolyester fibers are of the desired diameter and length. The exemplaryfiber production technique is based on pelletizing the PET bottles,melting the pellets to generate molten polyester, and passing the moltenpolyester through a screen or grating having predefined pore sizes (thepore sizes control the diameter of the resulting individual polyesterfibers). In a block 94, the polyester fibers are cut to the desiredlength. In an optional block 96, different fiber diameters and fiberlengths are combined according to a recipe empirically determined toenable a non-woven filter media having the desired MERV rating andpressure drop to be achieved. As described in detail below, in someembodiments only a single fiber diameter or fiber length is employed,thus the step of block 96 is not required in all embodiments. In a block98, the polyester fibers are carded (also referred to as combing) toalign the individual fibers. The aligned fibers are then used togenerate the PET derived polyester fiber based non-woven textile filtermedia in a block 100. Needle punching represents an exemplary techniqueto generate the recycled polyester fiber based non-woven textile filtermedia. In some embodiments, some amount of recycled synthetic fibersfrom other sources (such as shredded carpet, textiles, and clothing) canbe added to the PET derived polyester fiber. However, such othersynthetic fiber (generally a mixture of nylon and polyester) will likelynot exhibit the closely controlled diameters of the PET derivedpolyester fiber, and such other synthetic fiber is best used inmoderation. The cost of such other synthetic fiber is likely to be lowerthan the PET derived polyester fiber, but empirical testing has shownthat non-woven filter media produced solely from non PET derivedpolyester cannot achieve a pressure drop of under 2.9 PSI. In anexemplary embodiment, the PET derived polyester fiber is formed into anon-woven textile weighing about 0.15 to about 0.35 ounces per squarefoot. In at least one exemplary embodiment, the non-woven textile ofthat weight has a thickness that ranges from about 0.5 cm to about 2.5cm.

Having generally described the production of a non-woven filter mediaproduced primarily from PET derived polyester fiber, specific fiberrecipes (i.e., specific fiber diameters and fiber lengths) for producinga filter media exhibiting a pressure drop of less than 2.9 PSI will nowbe described.

In a first exemplary fiber recipe, the non-woven filter media isproduced from PET derived polyester fiber having the followingparameters: about 1.5 denier and about 1.5 inches (about 38 mm) inlength. In at least one embodiment, such a fiber recipe is formed into anon-woven textile weighing about 0.15 to about 0.35 ounces per squarefoot. In at least one exemplary embodiment, the non-woven textile ofthat weight has a thickness that ranges from about 0.5 cm to about 2.5cm.

In a second exemplary fiber recipe, the non-woven filter media isproduced from PET derived polyester fiber having the followingparameters: about 1.5 denier and about 3 inches (about 76 mm) in length.In at least one embodiment, such a fiber recipe is formed into anon-woven textile weighing about 0.15 to about 0.35 ounces per squarefoot. In at least one exemplary embodiment, the non-woven textile ofthat weight has a thickness that ranges from about 0.5 cm to about 2.5cm.

In a third exemplary fiber recipe, the non-woven filter media isproduced from PET derived polyester fiber having the followingparameters: 1.5 denier and fiber lengths ranging from about 5 mm toabout 100 mm. A substantial majority of the fibers preferably range fromabout 5 mm to about 55 mm in length, and most preferably, about 70% ofthe fibers fall into the aforementioned range of lengths. The length ofa minority of the fibers is in the range of from about 60 mm to about100 mm, and most preferably, less than about 30% of the fibers are inthis range. Regardless of the specific range employed, a substantialmajority of the fibers must be relatively shorter to provide the desiredlarge surface area, and the desired plurality of interstitial volumes orspaces. Also, regardless of the specific range of lengths of the fibers,sufficient relatively longer fibers are required to enable the resultingnon-woven textile to achieve a cohesiveness that enables a mat formedout of the fibers to exhibit sufficient structural stability towithstand the air flow rates used in air filtering applications. In atleast one embodiment, such a fiber recipe is formed into a non-woventextile weighing about 0.15 to about 0.35 ounces per square foot. In atleast one exemplary embodiment, the non-woven textile of that weight hasa thickness that ranges from about 0.5 cm to about 2.5 cm.

In a fourth exemplary fiber recipe, the non-woven filter media isproduced from PET derived polyester fiber having the followingparameters: about 4 denier and about 1.5 inches (about 38 mm) in length.In at least one embodiment, such a fiber recipe is formed into anon-woven textile weighing about 0.15 to about 0.35 ounces per squarefoot. In at least one exemplary embodiment, the non-woven textile ofthat weight has a thickness that ranges from about 0.5 cm to about 2.5cm.

In a fifth exemplary fiber recipe, the non-woven filter media isproduced from PET derived polyester fiber having the followingparameters: about 4 denier and about 3 inches (about 76 mm) in length.In at least one embodiment, such a fiber recipe is formed into anon-woven textile weighing about 0.15 to about 0.35 ounces per squarefoot. In at least one exemplary embodiment, the non-woven textile ofthat weight has a thickness that ranges from about 0.5 cm to about 2.5cm.

In a sixth exemplary fiber recipe, the non-woven filter media isproduced from PET derived polyester fiber having the followingparameters: 4 denier and fiber lengths ranging from about 5 mm to about100 mm. A substantial majority of the fibers preferably range from about5 mm to about 55 mm in length, and most preferably, about 70% of thefibers fall into the aforementioned range of lengths. The length of aminority of the fibers is in the range of from about 60 mm to about 100mm, and most preferably, less than about 30% of the fibers are in thisrange. Regardless of the specific range employed, a substantial majorityof the fibers must be relatively shorter to provide the desired largesurface area, and the desired plurality of interstitial volumes orspaces. Also, regardless of the specific range of lengths of the fibers,sufficient relatively longer fibers are required to enable the resultingnon-woven textile to achieve a cohesiveness that enables a mat formedout of the fibers to exhibit sufficient structural stability towithstand the air flow rates used in air filtering applications. In atleast one embodiment, such a fiber recipe is formed into a non-woventextile weighing about 0.15 to about 0.35 ounces per square foot. In atleast one exemplary embodiment, the non-woven textile of that weight hasa thickness that ranges from about 0.5 cm to about 2.5 cm.

In a seventh exemplary fiber recipe, the non-woven filter media isproduced from PET derived polyester fiber having the followingparameters: a combination of about 1.5 denier and about 4 denier fibers,and fiber lengths ranging from about 5 mm to about 100 mm. A substantialmajority of the fibers preferably range from about 5 mm to about 55 mmin length, and most preferably, about 70% of the fibers fall into theaforementioned range of lengths. The length of a minority of the fibersis in the range of from about 60 mm to about 100 mm, and mostpreferably, less than about 30% of the fibers are in this range.Regardless of the specific range employed, a substantial majority of thefibers must be relatively shorter to provide the desired large surfacearea, and the desired plurality of interstitial volumes or spaces. Also,regardless of the specific range of lengths of the fibers, sufficientrelatively longer fibers are required to enable the resulting non-woventextile to achieve a cohesiveness that enables a mat formed out of thefibers to exhibit sufficient structural stability to withstand the airflow rates used in air filtering applications. Acceptable ratios of the1.5 denier and 4 denier fibers respectively include 1:1, 2:1, 3:1, 4:1,1:2, 1:3, and 1:4 (as well as incremental ratios there between). In atleast one embodiment, such a fiber recipe is formed into a non-woventextile weighing about 0.15 to about 0.35 ounces per square foot. In atleast one exemplary embodiment, the non-woven textile of that weight hasa thickness that ranges from about 0.5 cm to about 2.5 cm.

In an eighth exemplary fiber recipe, the non-woven filter media isproduced from PET derived polyester fiber having the followingparameters: a combination of about 1.5 denier and about 4 denier fibers,and fibers about 3 inches in length. In at least one embodiment, such afiber recipe is formed into a non-woven textile weighing about 0.15 toabout 0.35 ounces per square foot. In at least one exemplary embodiment,the non-woven textile of that weight has a thickness that ranges fromabout 0.5 cm to about 2.5 cm.

In a ninth exemplary fiber recipe, the non-woven filter media isproduced from PET derived polyester fiber having the followingparameters: a combination of about 1.5 denier and about 4 denier fibers,and fibers about 1.5 inches in length. In at least one embodiment, sucha fiber recipe is formed into a non-woven textile weighing about 0.15 toabout 0.35 ounces per square foot. In at least one exemplary embodiment,the non-woven textile of that weight has a thickness that ranges fromabout 0.5 cm to about 2.5 cm.

With respect to any of the above recipes, other recycled (or virgin)synthetic fibers having relatively larger diameters can be added to therecipe in an amount not to exceed 50% (too much of this larger diameterfiber will reduce the cohesiveness of the resulting filter media). Usingabout 10% or less of the non PET derived fibers is more preferred.

Applicants previously developed a sorbent material based on textilewaste that had been shredded to reduce the waste material into fiberform. The resulting fiber mass included a mixture of delustered nylonand polyester fibers, and was a very effective absorbent material forremoving oil from water when processed into a nonwoven textile. Thenylon fibers averaged about 1.5 denier in diameter, and the polyesterfibers averaged about 4.5 denier in diameter. Significantly, thenon-woven textile filter media formed from such a fiber mixture was notvery successful as an air filter, because while the material had anacceptably high MERV rating of about 8, the pressure drop associated thefilter media could not be reduced below about 3.5 PSI (reducing thethickness of the non-woven texture material reduced the pressure dropsomewhat, but when the material was made lighter than about 4.5 ouncesper square yard, the nonwoven fabric disintegrated when exposed to airflow volumes normally used in HVAC applications; i.e., an air flow rateof about 1968 CFM).

Applicants discovered the surprising result that when diametercontrolled PET derived polyester fiber was used in place of the highlydelustered nylon and polyester fibers discussed above, the resultingnon-woven textile could be made significantly lighter than about 4.5ounces per square yard (as light as about 0.15 to about 0.35 ounces persquare foot), without disintegrating when exposed to air flow volumesnormally used in HVAC applications. Such a non-woven textile exhibited aMERV rating of about 8, and exhibited a pressure drop below 2.9.Significantly, these superior results were obtained when similar fiberlengths and similar fiber diameters were employed. Note that the recipesnoted above are based on PET derived polyester fiber having diametersbetween 1.5 D and 4 D, yet produced a non-woven textile with startlinglydifferent properties (i.e., the ability to maintain cohesiveness at muchlower fiber densities, and a significantly lower pressure drop when usedas a filter media for an air filter). The reasons for this surprisingresult are still being investigated, but it was decidedly unexpected.Initial testing has noted that the PET derived polyester fiber issignificantly less delustered than the nylon and polyester fibersderived from recycled textiles where the fibers had been delustered toaccept a dye. Delustering has been shown to have a beneficial impact ona fiber's ability to function as a filter media, as such delusteringgreatly increases the surface area of the fiber. The rough surfaces ofthe delustered fibers offer greater fiber to fiber traction betweenadjacent fibers, which should promote cohesion of a non-woven filtermedia formed of such fibers. Thus, applicants' discovery that the PETderived polyester fiber, whose individual fibers exhibit significantlyless delustering and significantly less surface area, actually enable amore cohesive non-woven textile to be achieved (as compared to non-woventextiles formed from highly delustered nylon and polyester fibersderived from recycled textiles where the fibers had been delustered toaccept a dye) is counter-intuitive and quite unexpected. An additionalbenefit of the use of the PET derived polyester fiber is that such lessdelustered fibers appear to reduce the air resistance of the non-woventextile based filter media formed out of such fibers, withoutsacrificing so much absorbent ability to reduce the material's abilityto achieve a relatively high MERV rating (i.e., a MERV rating of atleast about 8).

FIGS. 4A and 4B illustrate schematic representations of a relativelyshorter PET derived polyester fiber 12 and a relatively longer PETderived polyester fiber 14, pluralities of each of which are required insome of the fiber recipes disclosed herein. The exact proportions of theindividual fibers are not critical, though in an exemplary embodiment, amajority of the fibers are relatively short, while only a minority ofthe fibers are relatively long. The relatively shorter PET derivedpolyester fibers provide a great deal of surface area, while therelatively longer PET derived polyester fibers help bind the relativelyshorter fibers and relatively longer fibers together into a mass. In onepreferred embodiment, the relatively shorter fibers are on the order offrom about 5 mm to about 15 mm in length, while the relatively longerfibers are on the order of from about 85 mm to about 100 mm in length.Such an embodiment also includes a plurality of fibers of intermediatelength, ranging from about 15 mm to about 85 mm in length.

FIGS. 5A and 5B illustrate schematic representations of a relativelythick PET derived polyester fiber 22 and a relatively thin PET derivedpolyester fiber 24. In at least one exemplary embodiment of the conceptsdisclosed herein, a majority of the fibers are relatively thin, while aminority of the fibers are relatively thick. Using relatively morethinner fibers appears to reduce the pressure drop for the resultingnonwoven textile filter media. The relatively thick PET derivedpolyester fibers are on the order of about 40 μm in diameter (i.e.,about 4 D), while the relatively thin fibers are on the order of about15 μm in diameter (i.e., about 1.5 D). With respect to the length offibers, in at least one exemplary embodiment, a substantial majority ofthe PET derived polyester fibers are relatively short, while only aminority of the PET derived polyester fibers are relatively long. Inthis embodiment, the terms “long” and “short” generally relate to amidpoint in the specific range of lengths of the fibers that are used.Such a mixture of fiber lengths enhances the sorbency of the resultingnon-woven textile filter media. With respect to the relative diametersof the individual fibers, the diameters of the individual fibers requiresignificantly more control, and while the diameters do not significantlyaffect the sorbency of the resulting non-woven fiber material, thediameters do significantly affect the pressure drop of the non-woventextile produced using the PET derived polyester fibers. It should alsobe noted that fiber length and fiber diameter is a function ofprocessing, in that fibers can be processed to achieve a specificdesired range of lengths, and different screens (or sieves, or gratings)can be used to control fiber diameters of the PET derived polyesterfibers.

A network 30 of interlinking PET derived polyester fibers in accord withsome of the exemplary embodiments disclosed herein is schematicallyillustrated in FIG. 6. A plurality of relatively shorter PET derivedpolyester fibers 12 are intermingled with a plurality of relativelylonger PET derived polyester fibers 14. As noted above, a minority ofrelatively longer fibers 14 bind the mass of interleaved fibers (bothlong and short) together into the desired cohesive mass during needlepunching to generate the non-woven textile. FIG. 7 illustrates, in amagnified section 20 of network 30 of interlinking fibers, how network30 provides a sorbent that exhibits both adsorbent capabilities, as wellas absorbent capabilities. Contaminants, such as hydrocarbon products 40are adsorbed on individual surfaces of both relatively shorter PETderived polyester fibers 12 and relatively longer PET derived polyesterfibers 14. Hydrocarbon products 42 are absorbed into interstitial spaceswithin network 30, proximate to locations where relatively shorter PETderived polyester fibers 12 and relatively longer PET derived polyesterfibers 14 cross each other.

Tests of a non-woven textile based on a polyester fiber mixture indicatethat when incinerated, the residual ash was less than 1% (˜0.6%). TheU.S. Environmental Protection Agency has established guidelines forpreferred residual ash percentages for sorbent materials, and thoseguidelines indicate that up to 2% ash is acceptable. From a disposalstandpoint, the less ash generated by burning a sorbent material, thebetter, as the resulting ash must be hauled to a landfill. Without anyhydrocarbon having been sorbed, the polyester fiber mixture has athermal energy rating of about 7,600 British Thermal Units (BTU) perpound. In general, the higher the BTU value of a material, the morelikely that material is usable for energy production. The BTU value ofcoal varies substantially, and ranges from 10,000-15,000 BTU/pound. Inaddition to the PET derived polyester fiber filter media, the airfilters include a cardboard frame, and (in some embodiments) a polymermesh support member, each of which is suitable for disposal viaincineration. Thus, there is potential for disposing of the used airfilters by incineration that enables energy recovery. U.S. cement kilnsin particular are noted for their use of high BTU value waste materialsas supplementary fuels (the production of cement is a very energyintensive process).

As noted above, the PET derived polyester fibers are used to produce anon-woven textile to be used as a filter media (of course, such fiberscould be used to generate a woven textile, although the steps requiredto produce such a woven textile would be cost prohibitive; whereasnon-woven textiles can be fabricated at significantly lower costs). Onetechnique for producing a non-woven textile from the mixture ofrelatively longer and relatively shorter fibers disclosed herein is toprovide a “quilted” blanket of the material. A quilted sorbent blanket,as described herein and the claims that follow, is an encapsulatingenvelope produced in sizes and shapes of conventional sorbent blanketsthat includes a plurality of individual chambers, each filled with anamorphous mass of PET derived polyester fibers. These individualchambers are defined by a plurality of baffles, or by a plurality ofparallel channels. A baffle arrangement segments a quilted sorbentblanket into a plurality of quadrilateral segments joined (or quilted)together to form the blanket. Each baffle is separate from the otherbaffles, and contains a quantity of PET derived polyester fibers in anamorphous mass configuration. The encapsulating baffle is porous, so aircan pass through the baffle and contaminants can be sorbed by theencapsulated mass of PET derived polyester fibers. The purpose of theplurality of baffles is to ensure that the PET derived polyester fibermass remains evenly distributed throughout the quilted blanket, ratherthan clumping together at an end of the blanket. A channel configurationworks the same way, except the channels are generally elongate in shape,significantly narrower than baffles, and a single channel generally runsthe length of the quilted sorbent blanket. In a baffle configuration, aplurality of baffles are required to span the length of the blanket.Such baffles and channels are commonly used in producing downcomforters, to ensure that the down in such a comforter remains evenlydistributed, and retains a desired loft.

While needle punching represents an exemplary technique for producingthe desired non-woven textile filter media from the recycled PET derivedpolyester fiber, it should be noted that air laid processing can also beemployed. In such a process, some binder (such as a thermosettingadhesive) is added to the fibers, as they are air laid into a layeredstructure. The binder becomes mixed into the fiber mass, and as thebinder sets the non-woven textile is generated. The binder somewhatincreases the air resistance of the resulting non-woven textile, as wellas somewhat reduces the filtering ability of the resulting non-woventextile. However, too little binder will result in the non-woven textilebeing unable to withstand the required air flow. Thus, the amount ofbinder being used is balanced between the needs for achieving a filtermedia with a desired filtering efficiency and a desired cohesiveness.

In a more preferred embodiment of the concepts disclosed herein, the PETderived polyester fibers disclosed herein (i.e., the PET derivedpolyester fiber recipes noted above) are formed into a non-woventextile. The PET derived polyester fibers disclosed herein can be usedto form non-woven pads, filters, mats and blankets in a variety ofthicknesses, sizes, and shapes. One technique that is expected to beuseful in fabricating such non-woven textiles for use as a filter mediais needle punching, or needle weaving (also referred to as needlefelting). The sorbent fibers are placed on a fine mesh screen (sometimesreferred to as a scrim). A plurality of barbed needles are “punched”into the mass, so that the needles penetrate the fine mesh screen. Asthe needles are punched into the mass, and then withdrawn, some of thefibers are caught by the needles, and drawn through the mesh screen,binding the mass of fibers to the screen at a plurality of locations,both compressing the mass of fibers and securely affixing the mass offibers to the mesh screen. The resulting needle punched mat can be cutto a desired size or shape, and employed as the filter media in an airfilter.

Significantly, non-woven mats made from prior art recycled syntheticfibers have been unsuitable for use in air filters, due to therelatively high pressure drops associated with non-woven textiles formedout of such recycled synthetic fibers. Many of the prior art recycledsynthetic fibers have been bound together using binders or adhesives toprovide mechanical strength, and do not work well as sorbents, becausethe binders/adhesives reduces the sorbency of the mat. Note that using avery tight mesh to contain recycled synthetic fibers in a filter framedoes not work well, because when the mesh is sufficiently tight (i.e.,with small openings) to provide the necessary mechanical strength, themesh reduces flow rates to unacceptable levels (flow rate reductionsincrease energy costs, since more energy needs to be expended to force afluid through the filter).

If desired, the PET derived polyester fiber media included in the airfilters disclosed herein can be treated with at least one of aherbicide, a bactericide, a fungicide, an antimicrobial agent, adeodorizer (such as activated carbon, or other materials, to removeodors), and a fragrance (to introduce a pleasant scent into the filteredair). Furthermore, the PET derived polyester fiber filter media can alsobe treated with an electrostatic charge to temporarily increase its MERVvalue.

Other exemplary aspects of the concepts disclosed herein are as follows.The non-woven textile produced from the PET derived polyester fiber is,in at least some exemplary embodiments, both air and water permeable. Inat least some exemplary embodiments, the non-woven textile produced fromthe PET derived polyester fiber need not be combined with any otherfabric or textile for use as a filter media (except for the supportelement discussed above, which is generally not implemented as a textileor fabric). In at least some exemplary embodiments, the non-woventextile produced from the PET derived polyester fiber includes nobinders or adhesives, which could increase the air resistance of thefilter media, as well as reducing the sorbency of the filter media. Inat least some exemplary embodiments, the PET derived polyester fibers,nor any other fibers used in the non-woven textile filter media, arecoated with any material to enhance the fibers effectiveness as asorbent. In at least some exemplary embodiments, the nonwoven textileproduced from the PET derived polyester fiber is homogeneous, such thatany mixture of different fiber types, fiber diameters, and/or fiberlengths are relatively evenly distributed throughout the non-woventextile. In at least some exemplary embodiments, the non-woven textileproduced from the PET derived polyester fiber is not thermally bondedtogether to produce the non-woven textile, as such thermal bonding canundesirably change the interstitial spaces in the network of fibers thatdevelops during needle punching.

FIGS. 8A and 8B schematically illustrate air filters where supportstructure 86 exhibits a different configuration than that shown inFIG. 1. The support structures of FIGS. 8A and 8B can be formed ofmetal, plastic or cardboard. In at least one embodiment, such supportstructures are formed of recycled materials. If desired, the supportstructures of FIGS. 8A and 8B can be formed integral to the frame 82.

Although the concepts disclosed herein have been described in connectionwith the preferred form of practicing them and modifications thereto,those of ordinary skill in the art will understand that many othermodifications can be made thereto within the scope of the claims thatfollow. Accordingly, it is not intended that the scope of these conceptsin any way be limited by the above description, but instead bedetermined entirely by reference to the claims that follow.

The invention in which an exclusive right is claimed is defined by thefollowing:
 1. An air filter comprising: (a) a frame; and (b) a non-woventextile filter media disposed in the frame, the nonwoven textile filtermedia comprising longer fibers and shorter fibers, wherein the shorterfibers range from 5 to 55 mm in length and make up a majority of thenonwoven textile filter media and the longer fibers range from 60 to 100mm in length and make up a minority of the nonwoven textile filtermedia, the longer fibers and shorter fibers comprise polyester fibers,wherein the polyester fibers comprise a combination of about 1.5 denierfibers and about 4 denier fibers, and wherein a ratio of 1.5 to 4 denierfibers is from about 1:1 to about 1:4.
 2. The air filter according toclaim 1, wherein the non-woven textile filter media comprises a waddedmass that has been formed via needle punching, felting, thermal bonding,air laid processing or a combination thereof.
 3. The air filteraccording to claim 1, wherein the non-woven textile filter media is inthe form of a flat panel or is pleated.
 4. The air filter according toclaim 1, wherein the non-woven textile filter media comprises recycledpolyester.
 5. The air filter according to claim 1, wherein non-woventextile filter media weighs from about 0.15 to about 0.35 ounces persquare foot.
 6. The air filter according to claim 1, wherein non-woventextile filter media has a thickness of from about 0.5 to about 2.5 cm.7. The air filter according to claim 1, further comprising a meshsupport.
 8. The air filter according to claim 7, wherein the meshsupport is formed of metal, plastic, cardboard or a composite thereof.9. The air filter according to claim 1, wherein the non-woven textilefilter media further comprises a thermosetting adhesive.
 10. The airfilter according to claim 1, wherein the non-woven textile filter mediais treated with an herbicide, a bactericide, a fungicide, anantimicrobial agent, a deodorizer, a fragrance, or a combinationthereof.
 11. A method for filtering air, comprising: (a) providing anair filter; and (b) introducing the air filter into an air flow, suchthat the air filter filters the air, wherein the air filter comprises:(i) a frame; and (ii) a non-woven textile filter media disposed in theframe, the nonwoven textile filter media comprising longer fibers andshorter fibers, wherein the shorter fibers range from 5 to 55 mm inlength and make up a majority of the nonwoven textile filter media andthe longer fibers range from 60 to 100 mm in length and make up aminority of the nonwoven textile filter media, the longer fibers andshorter fibers comprise polyester fibers, wherein the polyester fiberscomprise a combination of about 1.5 denier fibers and about 4 denierfibers, and wherein a ratio of 1.5 to 4 denier fibers is from about 1:1to about 1:4.
 12. The method according to claim 11, wherein thenon-woven textile filter media is in the form of a flat panel or ispleated.
 13. The method according to claim 11, wherein non-woven textilefilter media weighs from about 0.15 to about 0.35 ounces per squarefoot.
 14. The method according to claim 11, wherein non-woven textilefilter media has a thickness of from about 0.5 to about 2.5 cm.
 15. Themethod according to claim 11, wherein the air filter further comprisinga mesh support.
 16. A method for making a non-woven textile filter mediafor filtering air, comprising: (a) providing a quantity of bulkpolyester; (b) generating a quantity of polyester fiber having apredefined diameter from the quantity of bulk polyester; (c) cutting thepolyester fiber to a predefined length; and (d) generating a non-woventextile filter media from the polyester fiber via needle punching,felting, thermal bonding, air laid processing or a combination thereof,wherein the non-woven textile filter media comprises longer fibers andshorter fibers, wherein the shorter fibers range from 5 to 55 mm inlength and make up a majority of the nonwoven textile filter media andthe longer fibers range from 60 to 100 mm in length and make up aminority of the nonwoven textile filter media, wherein the polyesterfibers comprise a combination of about 1.5 denier fibers and about 4denier fibers, and wherein a ratio of 1.5 to 4 denier fibers is fromabout 1:1 to about 1:4.
 17. The method according to claim 16, whereinthe non-woven textile filter media is in the form of a flat panel or ispleated.
 18. The method according to claim 16, wherein non-woven textilefilter media weighs from about 0.15 to about 0.35 ounces per squarefoot.
 19. The method according to claim 16, wherein non-woven textilefilter media has a thickness of from about 0.5 to about 2.5 cm.
 20. Themethod according to claim 16, wherein the non-woven textile filter mediafurther comprises a thermosetting adhesive.